Vehicle security systems are widely used to deter vehicle theft, prevent theft of valuables from a vehicle, deter vandalism, and to protect vehicle owners and occupants. A typical automobile security system, for example, includes a central processor or controller connected to a plurality of vehicle sensors. The sensors, for example, may detect opening of the trunk, hood, doors, windows, and also movement of the vehicle or within the vehicle. Ultrasonic and microwave motion detectors, vibration sensors, sound discriminators, differential pressure sensors, and switches may be used as sensors. In addition, radar sensors may be used to monitor the area proximate the vehicle.
The controller typically operates to give an alarm indication in the event of triggering of a vehicle sensor. The alarm indication may typically be a flashing of the lights and/or the sounding of the vehicle horn or a siren. In addition, the vehicle fuel supply and/or ignition power may be selectively disabled based upon an alarm condition.
A typical security system also includes a receiver associated with the controller that cooperates with one or more remote transmitters typically carried by the user as disclosed, for example, in U.S. Pat. No. 4,383,242 to Sassover et al. The remote transmitter may be used to arm and disarm the vehicle security system or provide other remote control features from a predetermined range away from the vehicle.
As disclosed in U.S. Pat. No. 5,049,867 to Stouffer and U.S. Pat. No. 5,146,215 to Drori, the security system controller may include features to store and compare unique codes associated with a plurality of remote transmitters, each remote transmitter having its own unique code initially programmed therein. U.S. Pat. No. 5,146,215 in particular discloses that remote transmitter codes may be added or deleted from the controller corresponding to the number of remote transmitters desired by the user. Unfortunately, a would-be thief gaining access to the controller may readily enter the program or learn mode and install the code of an unauthorized remote transmitter. The owner would thus be unaware of such activity, until the thief returns with the unauthorized remote transmitter to disarm the security system and steal the vehicle, or steal the vehicle contents.
Also related to remote control of a vehicle function U.S. Pat. No. 5,252,966 to Lambropoulous et al. discloses a remote keyless entry system for a vehicle. The keyless entry system permits the user to remotely open the vehicle doors or open the vehicle trunk using a small handheld transmitter. The system provides a thirty second time window in which to operate one or more uniquely coded remote transmitters to load the transmitter codes into memory. If someone desired to surreptitiously record a new transmitter code into someone else's receiver, the new code would overwrite the prior codes so that only the new code would remain. If the authorized transmitter ceased to operate, the user may recognize that the receiver had been the subject of tampering. Unfortunately, the user may also simply assume that the battery in his remote transmitter had failed and would be unaware that a new transmitter had been coded into the system without his knowledge.
Remote vehicle starting systems also typically include uniquely coded remote transmitters capable of remotely starting the vehicle engine, and wherein the transmitter codes may be learned into the system. Other remote control systems for a vehicle operate similarly, and are subject to tampering or bypassing by one gaining access to the controller to record a different unauthorized transmitter code. Unfortunately, the user may be completely unaware that a new transmitter has been coded and may operate the remote control system, until, for example, a thief returns with a coded remote transmitter, disarms the security system and steals the vehicle.